This 80287-compatible chip was developed from the Cyrix 83D87 and has been available since 1991. It complies completely with the IEEE-754 standard for floating-point arithmetic and features nearly total compatibility with Intel's coprocessors, including implementation of the full Intel 80387 instruction set. It implements the transcendental functions with the same degree of accuracy and the superior speed of the Cyrix 83D87. This makes the Cyrix 82S87 the fastest and most accurate 287 compatible coprocessor available.
Documentation by Cyrix rates the 82S87 at 730 kWhets/sec for a 12.5 MHz system, while the Intel 287XL performs only 552 kWhets/sec. 82S87 chips manufactured after 1991 use the internals of the Cyrix 387+, which succeeds the original 83D87.

The CX-83D87 was introduced in 1989. It is the fastest 387-compatible coprocessor and provides up to 50% more performance than the Intel 387DX. The 83D87 also offers the most accurate transcendental functions of all coprocessors. It is the 387 clone with the highest degree of compatibility to the Intel 387DX. Unlike the Intel 387DX, the 83D87 (and all other 387-compatible chips as well) does not support asynchronous operation of CPU and coprocessor. To reduce power consumption the 83D87 features advanced power saving features. Those portions of the coprocessor that are not needed are automatically shut down. If no coprocessor instructions are being executed, all parts except the bus interface unit are shut down.

Cyrix 387DX-33

387DX
387DX-33
(C)(M) 1989 Cyrix USA DC2068

The predecessor of the CX-83D87. The Cyrix 387DX was soon replaced by the much more advanced CX-83D87

The Cyrix 387DX+ is a CX-83D87 for the European marked, relabeled 387DX+. It is the fastest 387-compatible coprocessor and provides up to 50% more performance than the Intel 387DX. It also offers the most accurate transcendental functions of all coprocessors and is the 387 clone with the highest degree of compatibility to the Intel 387DX.

The 83S87 is the SX version of the Cyrix 83D87. Just as the 83D87 is the fastest 387-compatible coprocessor, the Cyrix 83S87 is the fastest of the 387SX compatible coprocessors, as well as providing the most accurate transcendental functions. 83S87 chips manufactured after 1991 use the internals of the Cyrix 387+, the successor to the original 83D87. The Cyrix 83S87 is ideally suited to be used with the Cyrix Cx486SLC CPU, a 486SX compatible CPU which is a replacement chip for the Intel 386SX CPU.
The 83S87 is packaged in a 68-pin PLCC and is available in 16, 20, 25, and 33 MHz versions. Due to the advanced power saving features of the Cyrix coprocessor, the typical power consumption of the 20 MHz version is only about 350 mW, while maximum power dissipation is 1.6 W.